(a) Field of the Invention
The present invention relates to a liquid crystal display having a wide viewing angle, and more particularly, to a liquid crystal display of which viewing angle is made wide by patterning apertures in electrodes.
(b) Description of the Related Art
Liquid crystal displays (LCDs) typically include two substrates and a liquid crystal layer interposed between the substrates. The transmittance of light is controlled by the intensity of an electric field applied to the liquid crystal layer.
In a vertically aligned (VA) mode LCD, liquid crystal molecules take on a homeotropic orientation in which long axes of the molecules are perpendicular to the substrate. This configuration cuts off lights almost completely in an “off” state where an electric field above a certain value is not applied to the liquid crystal layer. In the normally black mode, since brightness in the off state is extremely low, a significantly higher contrast ratio can be obtained when compared to the conventional twisted nematic LCDs. However, in an “on” state, in which an electric field above a certain value is applied between the electrodes, a tilt direction of the liquid crystal molecules is irregular such that a direction of the long axes of some liquid crystal molecules becomes identical to a polarizing direction of either an upper or a lower polarizer film. When this occurs, the liquid crystal molecules are unable to rotate the polarizing direction of light, thereby blocking the light with the polarizer films. These parts of the LCD appear black, degrading the picture quality. To solve this problem, many methods of patterning electrodes are proposed. In U.S. Pat. No. 5,136,407, a method of forming line-shaped apertures on electrodes of one of the two substrates is disclosed. In U.S. Pat. No. 5,309,264, there is disclosed a method of forming ″X-shaped apertures on transparent electrodes of one of the two substrates.
In order to maintain a storage capacitance, either storage lines or gate lines are used. In the latter case, an aperture formed at a pixel above a gate may form an electric field between the gate line and a common electrode and leak lights by moving the liquid crystal material, when a voltage is applied to the gate line. This limits the design of the apertures of the electrodes. Accordingly, it is hard to design an electrode pattern that allows a bigger margin for pixel alignment. Further, in a ring gate structure, it frequently causes a high pixel defect, which leaves pixels continuously in a white state as a result of shorting the pixel electrodes with the data lines or the gate lines. This problem is difficult to repair. Finally, an aperture ratio is low since light can not be transmitted in the areas where the gate lines are formed.